Conductive polyurethane foam compositions containing tetralyanoethylene and method

ABSTRACT

An electrically conductive polyurethane foam product is prepared by the in situ combination of polyurethane-forming reactants and an effective amount of a charge transfer agent selected from the group consisting of tetracyanoethylene (TCNE), picric acid and analogs thereof, for lowering electrical resistance of the foam product to less than 1×10 12  ohms. In a preferred embodiment, the conductive foam product is reticulated to a void volume of more than 80% after completion of the foam forming reaction.

This application is a continuation-in-part of U.S. patent applicationSer. No. 051,949 filed 5/19/87, now abandoned.

The present invention relates to three-dimensional expanded polyurethanefoam materials, such as flexible reticulated polyurethane foamcompositions, that are electrically conductive and have antistaticproperties. More specifically the invention relates to a polyurethanefoam having long-lasting and reliable electrical conductivitycharacteristics and a volume resistivity of approximately 10¹² ohm cm orless. This foam is produced by combining conventional polyurethanefoam-forming reactants and an effective amount of a charge transferagent such as the electron acceptor compound tetracyanoethylene (TCNE),picric acid and analogs thereof, under foam-forming conditions. In onepreferred embodiment, the conductive foam is subsequently reticulated bymomentary exposure to high temperature.

The analogs, according to the invention, have the formula AR-X^(m)-Y^(n), where AR is a radical selected from the group consisting ofbenzene, toluene and naphthalene; X is selected from the groupconsisting of OH, OCH₃, CH₂ OH, NH₂, NHCOCH₃, CN, and O-M, where M is analkalai metal salt of sodium or potassium; Y is selected from the groupconsisting of NO₂ and COCH₃ ; m is 1 or 2; and n is from 1 to 3.

BACKGROUND OF THE INVENTION

Reticulated polyurethane foam products have been used for many years asexplosion suppression materials in the fuel tanks and containers ofgasoline and kerosene powered vehicles. The reticulated foam is a threedimensional plastic material consisting of a plurality of strands whichare interconnected at spaced apart points to define void spaces orpores. The product generally has a void volume of more than 80% andpreferably more than 90%. The reticulated foam material is installedinside the fuel tank to occupy between about 50% and 100% of theinterior dimensions of the tank and serves to inhibit the rapid anduncontrolled spread of a flame front when a spark is introduced into thefuel mixture. Thus, polyurethane foams and foam linings are recognizedas an important safety feature in combustion technology, especially inthe fuel tanks of military and racing vehicles which are often operatedunder incendiary or static electric discharge conditions. Thereticulated urethane foam minimizes the danger of fire or explosionresulting from exposure to static electric discharges which often occurduring operation or fueling, or as the result of sparks that may begenerated in crashes.

Within a fuel containment area provided with a reticulated polyurethanefoam, fuel is often subject to vibration and turbulent motion. The foamtends to suppress fuel agitation due to vehicular motion, but staticcharges can build up within the tank or containment area until theyovercome air resistance, and dangerous static electricity discharges canoccur, for example during a refueling operation. A static discharge, forexample between an ungrounded fuel hose nozzle and the metal frame ofthe vehicle or tank, can damage sensitive electrical equipment, orworse, can trigger an explosion within the tank. This problem isrecognized in Martel et al., Static Charge in Aircraft Fuel Tanks,Technical Report No. AFWAL-TR-80-2049 (September, 1980). Therefore,there is a definite if not urgent need for reliable and long-lastingmeans for safely controlling static charges in the vicinity ofcombustion fuels and fuel gases, especially during fueling operations.

The polyurethane foams conventionally used as fuel tank filler materialsare non-conductors having high electrical resistivity, e.g., a volumeresistivity of greater than 10¹³ ohm cm. Therefore, they cannotdissipate or control static charges. Indeed, the high resistivity ofconventional foams may contribute to internal explosions caused bystatic build-up and discharge, even while tending to suppress or containexplosions.

Antistatic polyurethane foams which seek to achieve this purpose areknown. Unfortunately, the known compositions and methods suffer fromdegradation and failure because they rely on antistatic agents that arenot permanent; they are too easily removed from the foam structure bywashing or by mechanical abrasion, or they degrade rapidly with normalaging and become ineffective as antistatic materials.

One commercially available antistatic flexible foam is produced byincorporating quaternary amines into the foam as an additive, byswelling the finished foam, as described for example in Volz, U.S. Pat.No. 4,578,406; or by using post foaming topical coatings such asconductive carbon-containing surface coatings, described as prior art inthe Volz disclosure. Both of these known compositions and methods havecertain drawbacks, such as poor resistance to extraction by washing andlack of resistance to mechanical abrasion. Moreover, these prior artfoam compositions require a post-foaming treatment in order to impartgood electrical conductivity to the foam, i.e. a relatively lowelectrical resistivity on the order of 10¹² ohm cm or less.Additionally, some of the known antistatic foams can be very sensitiveto humidity.

Fuji et al., U.S. Pat. No. 3,933,697 discloses an antistaticpolyurethane foam containing a quaternary ammonium salt as theantistatic agent. Although the Fuji patent indicates that the quaternaryadditive can be incorporated into the foam forming reactants, it hasbeen found that foams which depend upon quaternary salts for theirelectrical conductivity properties do not retain such properties whenthe foam is exposed to aqueous or solvent solutions for extended periodsof time. Indeed, the known quaternary salts are water soluble, and washtoo readily from the foam.

Berbeco, U.S. Pat. No. 4,301,040 discloses a conductive polyurethanefoam incorporating finely divided conductive particles. However, it hasbeen found that the addition of an effective antistatic amount of finelydivided conductive particles results in severe deterioration of thephysical properties of the foam material. Foams of sufficiently lowresistivity to provide satisfactory electrical conductivity orantistatic properties (less than 10¹² ohm cm) are difficult to obtainusing known procedures and tend to lose their antistatic electricalproperties upon exposure to high humidity or solvents.

Other conductive compounds are known to be useful in combination withsolid polymers, including polyurethane resins, as opposed topolyurethane foams. For example, British Pat. No. 1,158,384; and (R.Knoesel et. al.) Bul. Soc. Chim. Fr. 1969 (1) 294-301, disclose the useof ethenetetracarboxy nitrile, also known as tetracyanoethylene (TCNE)to increase the conductivity of special donor polymer resins such aspolydimethylaminostyrene and polyvinylphenothiazine.

German Offenlegungsschrift 28 38 720 discloses selectively conductivesolid epoxide or polyurethane casting resins containing TCNE. Thisreference teaches that TCNE can effect the electrical conductivity ofsolid synthetic resins as electron acceptors. Solid epoxy orpolyurethane resins can be combined with TCNE, and the TCNE polyurethaneresin compositions are shown to have an electrical conductivity of about0.38×10-¹⁰ (ohm cm)⁻¹, which corresponds to a resistivity of 2.6×10¹⁰ohm cm.

These patents do not disclose or suggest that TCNE or picric acid can becombined in situ with foam-forming ingredients as charge transferagents, to form a conductive polyurethane foam product, nor is there anysuggestion that such a foam product could retain its electricalconductivity properties during the exothermic foam forming reaction (inwhich reaction temperatures may reach 300° F. or higher for severalhours) or the subsequent thermal reticulation treatment in which thesolidified foam mass is exposed to momentary plasma level temperaturesexceeding 2000° C. and the internal temperature of the foam material mayreach 400° F. or more.

While the use of conductivity enhancing electron acceptor compounds(charge transfer agents) such as TCNE in solid polyurethane resins isknown, the permanent and in situ incorporation of TCNE or picric acidwith polyurethane foam reactants to form a permanent electricallyconductive polyurethane foam having a resistivity of less than about10¹² ohm cm is not disclosed or suggested by the prior art.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an electrically conductivepolyurethane foam that is suitable for use as a filler material in fuelcontainers or tanks, particularly in vehicles having combustion poweredengines.

It is another object of the invention to provide a method for the insitu preparation of an electrically conductive polyurethane foam.

It is yet another object of the invention to provide a stable, reliableand long-lasting electrically conductive reticulated polyurethane foamstructure that retains its conductivity characteristics despite repeatedmechanical abrasion and exposure to heat, organic, and aqueous fluids.

A further object of the present invention is to provide an electricallyconductive reticulated polyurethane foam having void volume greater thanat least about 80%, and preferably more than 90%, using relatively smallquantities of the agent conferring electrical conductivity in the foamforming reaction mixture.

Another object of the invention is an electrically conductive thermallyreticulated polyurethane foam prepared from a polyol and an isocyanateand containing about 0.02 to 2.5 parts of TCNE per hundred parts byweight of polyol (php) in the foam forming mixture.

Another object of the invention is an electrically conductive thermallyreticulated polyurethane foam prepared from a polyol and an isocyanateand containing about 0.02 to 2.5 parts of picric acid per hundred partsby weight of polyol (php) in the foam forming mixture.

It is another object of the invention to provide a polyurethane foamcomposition having a non-degrading electrical volume resistance of lessthan about 10¹² ohm cm and preferably less than 10¹¹ ohm cm.

These and other objects of the invention will be apparent to skilledpractitioners in the art from the following disclosure.

The objects of the invention are achieved by providing an electricallyconductive polyurethane foam, wherein the electrical resistivity of thefoam is desirably decreased to approximately 10¹² ohm cm or less by theintegral incorporation of relatively small yet effective quantities of acharge transfer agent selected from the group consisting of TCNE, picricacid and analogs thereof, into the structure of the foam during foamformation.

Advantageous polyurethane foam forming reactants include well-knownpolyester and polyether polyols and diisocyanate compounds. Additionalreaction materials include water, catalyst compounds, and cell controlagents. According to the invention, the effective amount of chargetransfer agent (e.g., TCNE or picric acid) ranges from about 0.02 to 2.5parts per hundred parts polyol (php), preferably 0.1 to 0.5 php.Conductivity may be further enhanced by the incorporation of carbonblack pigment into the foam forming reaction mixture, when TCNE is thecharge transfer agent.

Surprisingly, the electrical conductivity properties afforded by in situincorporation of TCNE or picric acid survive the exotherm (on the orderof about 300° F.) accompanying polyurethane foam formation, subsequentreticulation of the foam under plasma temperature conditions (of about2000° C. or more), mechanical abrasion and long-term exposure to aqueousand organic fluids. Accordingly, the foam products of the invention areparticularly well suited for use as an antistatic material, for exampleas a filler in aircraft fuel tanks or as a packaging material fordelicate electronic components.

According to the invention, a conductive polyurethane foam is foamed insitu, by known means, using conventional foam forming reactantscomprising one or more polyols, an isocyanate compound or composition,and an effective amount of a charge transfer agent selected from thegroup consisting of TCNE, picric acid and analogs thereof, for providingsaid polyurethane foam with an electrical resistance of less than 1×10¹²ohm cm in a suitable solvent. The optional presence of finely dividedcarbon black pigment has been found to further enhance the electricalconductivity of polyurethane foam made in accordance with the presentinvention. The polyurethane foam materials of this invention containabout 0.02 to 2.5 php of charge transfer agent (e.g., TCNE), 2.5 phpbeing about the highest effective amount which can be incorporated intothe foam reactants without adversely affecting the physical propertiesof the foam material unrelated to its electrical conductivity, such asdensity and firmness. Preferably, the foam forming reactants containfrom 0.1 to 0.5 php of charge transfer agent, 0-2.2 php of carbon andpreferably 0.7-1.5 php of carbon may be optionally incorporated in thefoam. The optional carbon material is preferably added to thepolyurethane foam forming reactants in the form of a dispersion offinely divided carbon in the polyol or a low viscosity resin e.g.,propoxylated ethoxylated glycerin or polydiethylene adipate.

According to the present invention a polyether or polyester urethanefoam is formed from isocyanate and hydroxyl containing (polyol)reactants by known means, but with the charge transfer agentincorporated into the reaction mixture prior to foam formation. Theresulting polyurethane foam may thereafter be reticulated to a voidvolume of greater than 80% and preferably more than 90% if desired,preferably for example according to the thermal reticulation methodtaught in Geen et al., U.S. Pat. No. 3,175,025 which is incorporatedherein by reference. In preparing electrically conductive polyurethanefoams for use as fuel tank filler materials, graft polyols are preferredas the polyol constituent of the foam. One preferred graft copolymer isan ethylene oxide propylene oxide ether of glycerin to which a copolymerof styrene and acrylonitrile has been grafted. The invention is notlimited, however, to use of these graft materials as the polyolconstituent. The flexible three dimensional polyurethane foams of theinvention may be prepared by reacting isocyanate compounds withpolyether polyols, polyester polyols, mixtures of polyether andpolyester polyols, or with mixtures of polyether polyols and copolymerpolyols such as for example the grafted polyether containing styrene andacrylonitrile as described above, in the presence of the charge transferagent (TCNE, picric acid, etc.). The resulting electrically conductivepolyurethane foams exhibit a resistivity of less than 10¹² ohm cm, andretain this advantageously decreased electrical resistivity despiteexposure to exothermic foam forming conditions, relatively violent hightemperature reticulation procedures, immersion in water or fuel, and dryheat aging.

The charge transfer agent that is incorporated into the foam in situ,according to the invention, is at least one of TCNE, picric acid, and acompound of the formula

    AR-X.sup.m -Y.sup.n,

where

AR is a radical selected from the group consisting of benzene, tolueneand naphthalene;

X is selected from the group consisting of OH, OCH₃, CH₂ OH, NH₂,NHCOCH₃, CN, and O-M, where M is an alkalai metal salt of sodium orpotassium;

Y is selected from the group consisting of NO₂ and COCH₃ ;

m is an integer of 1 or 2; and

n is an integer from 1 to 3.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the surface resistivity of TCNE foam as afunction of in situ TCNE concentration.

FIG. 2 is a graph showing the volume resistivity of TCNE foam as afunction of in situ TCNE concentration.

FIG. 3 is a graph showing the effect on electrical conductivity ofadding carbon back to TCNE polyurethane foams.

FIG. 4 is a graph showing the volume resistivity of picric acid foam asa function of in situ picric acid concentration.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described with reference to a number of examples andembodiments, and with reference to a number of comparative tests. Itwill be understood by skilled practitioners that these examples,embodiments and comparisons are illustrative only, and do not limit thescope of the invention.

The polyurethane foams of the present invention may be prepared usingthe one shot or the pre-polymer methods that are well known to the artand in which hydroxyl containing ingredients (polyols) andpolyisocyanates are combined in the presence of well known catalysts,blowing agents, foam stabilizers, flame retardants, pigments andextenders. Polyester based polyurethanes, polyether based polyurethanes,copolymer polyol based polyurethanes and mixtures of them may be used inmaking the conductive foams of the invention, although polyether foamsare preferred.

The polyisocyanate ingredients that are useful in the present inventioninclude, but are not limited to, toluene diisocyanate (TDI), which ispreferred, and polymers of diphenylmethane 4,4' diisocyanate (MDI).

Representative hydroxyl containing ingredients for use in the inventioninclude polyester and polyether polyols such as, for example, thepolypropylene glycol adipate glycerine ester and the ethylene oxidepropylene oxide ether of glycerin. Graft copolymers of hydroxylcontaining constituents which may also be employed as polyolconstituents in practicing the invention include ethylene oxidepropylene oxide ether of glycerin to which various amounts (between 20and 40%) of a copolymer of styrene and acrylonitrile have been grafted.The preferred graft polyol for use in the present invention is a polymerconsisting of the ethylene oxide propylene oxide ether of glycerin towhich 20% of a copolymer of styrene and acrylonitrile has been grafted.

It has been surprisingly found that better electrical conductivityproperties are obtained using non-grafted polyols, when TCNE is thecharge transfer agent. Thus, the electrical conductivity of urethanefoams made using an ethylene oxide propylene oxide ether of glycerin asthe hydroxy containing constituent yields foams having an electricalresistivity of 2×10¹⁰ ohm cm, (e.g., using 0.2 php TCNE) while foamsprepared with a ethylene oxide propylene oxide ether of glycerincopolymerized with 40% of a styrene and acrylonitrile copolymer have anelectrical resistance of 3×10¹¹ ohm cm.

According to the invention, polyether or polyester polyols are reactedin situ under the usual polyurethane foam forming conditions with anisocyanate and from 0.02 to 2.5 php (preferably 0.1 to 0.5 php) of acharge transfer agent selected from the group consisting of TCNE, picricacid and analogs thereof. The foam forming reaction is conducted in thepresence of the usual foam forming ingredients including catalystcompounds (such as tertiary amines and organo tin compounds) cellcontrol agents and water to provide a polyurethane foam having anelectrical resistivity of about 10¹² ohm cm or less. The electricallyconductive polyurethane foam product may be advantageously reticulated,so that the foam product has a void volume of at least 80% andpreferably more than 90%, with the thermal reticulation technique taughtin Geen U.S. Pat. No. 3,750,025. In this procedure the three dimensionalfoam product is placed in a sealed gas-filled chamber filled with acombustible gas and the gas ignited to produce an explosion and a flamefront in which the foam is exposed to momentary plasma temperatures inexcess of 2000° C.

It has been found that polyurethane foams made with in situ chargetransfer agents are stable and retain their enhanced electricalconductivity properties after exposure to elevated temperatures (284° F.for 28 days) and long term immersion in aqueous and organic liquids attemperatures up to 200° C.

The invention will be illustrated in the following tables and workingexamples. With reference to the tables, foam formulations are based on100 parts by weight of polyol, as is customary. All other components areadded in parts by weight per hundred parts by weight of polyol (php),unless otherwise noted. "E n" is a convenient shorthand notation for theexpression: "x 10^(n)." Following is an identification of some of thematerials used in the working examples.

CEF is Tris chlorethyl phosphate (available from Stauffer Chemicals asFyrol CEF)

DPG is Dipropylene glycol

PCF is Tris chloroisopropyl phosphate available from Stauffer ChemicalCorp.

TDI 80/20 is an 80%/20% mixture of 2,4-diisocyanatomethylbenzene and2,6-diisocyanatomethylbenzene commonly called toluene diisocyanate (or80/20 TDI).

TDI 70/30 is a 70%/30% mixture of 2,4-diisocyanatomethylbenzene and2,6-diisocyanatomethylbenzene commonly called toluene diisocyanate (or70/30 TDI).

EXAMPLE 1 Manufacture of Electrically Conductive TCNE Foams

A wide variety of polyurethane foam compositions containing TCNE as thecharge transfer agent can be prepared, as illustrated below.

Formula 1(A)

A polyurethane antistatic foam was prepared by admixing the followingingredients on a conventional polyurethane foaming machine:

    ______________________________________                                        Material                     Parts                                            ______________________________________                                        Pluracol 718 - a standard 3000 molecular weight                                                            100                                              ethoxylated propoxylated glycerin polyol                                      manufactured by BASF.                                                         Goldschmidt Silicone 8028 is a silicone surfactant                                                         1.0                                              manufactured by Goldschmidt Corp., Hopewell, Virginia                         Water                        4.1                                              Union Carbide Amine Catalyst A-1                                                                           2.1                                              M & T Tin Catalyst T-125 - a dibutyl tin dialkyl                                                           1.4                                              acid manufactured by M & T Chemicals, Inc.,                                   Rahway, New Jersey                                                            Carbon Pigment - an 18% dispersion of carbon in                                                            7.7                                              polyether polyol. (Dispersion 4824 manufactured                               by Pigment Dispersions Inc., Edison, N.J.)                                    5% solution of TCNE in CEF   40.0                                             TDI 80/20                    40.4                                             ______________________________________                                    

The resulting foam product was not reticulated after foam formation, buthad a surface resistivity of 3.1 E 9 ohms/square and a volumeresistivity of 2.2 E 9 ohm cm.

Formula 1(B)

A graft antistatic foam was prepared using the following formulation.

    ______________________________________                                        Material                    Parts                                             ______________________________________                                        Pluracol 994 is a graft polyol, (40%)                                                                     100                                               acrylonitrile styrene copolymer) grafted on a                                                             100                                               ethoxylated propoxylated glycerine (M W 5600)                                 manufactured by BASF.                                                         Union Carbide Silicone L6202 is a silicone                                                                1.2                                               surfactant manufactured by Union Carbide.                                     Water                       4.6                                               Witco Tin Catalyst UL29 - is Diethyl tin mercaptide                                                       0.3                                               manufactured by Witco Chemical Corp., Chicago, Ill.                           Dabco 33LV - a 33% solution of triethylene diamine                                                        0.4                                               in dipropylene glycol, manufactured by Air Products                           & Chemicals, Inc., Allentown, Pennsylvania                                    5% solution of TCNE in PCF  4.0                                               TDI 80/20                   51.0                                              ______________________________________                                    

The non-reticulated foam had a resistivity of 3.2 E 11 ohm cm.

Formula 1(C)

A polyester antistatic foam was prepared using the followingformulation:

    ______________________________________                                        Material                      Parts                                           ______________________________________                                        F-76 Resin - a hydroxyl terminated ester resin -                                                            100                                             specifically glycerin adipate polyoxyethylene,                                manufactured by Witco Chemical Corp.                                          TDI 70/30                     47.3                                            L536 - a silicone surfactant manufactured by Union                                                          1.2                                             Carbide.                                                                      Water                         3.7                                             N--Cocomorpholine             1.6                                             Amine Catalyst - Thancat M-75 a proprietary                                                                 1.2                                             tertiary amine, manufactured by Texaco Chemical Co.,                          Bellaire, Texas                                                               Amine Catalyst ADMA-6 - hexadecyl dimethyl amine,                                                           0.5                                             manufactured by Ethyl Corp., Houston, Texas                                   5% solution of TCNE in PCF    6.0                                             ______________________________________                                    

This foam had a surface resistivity of 3.6 E 11 ohms/square and a volumeresistivity of 2.8 E 10 ohm cm. Moreover, when tested at 15% relativehumidity the foam had a static decay time (5000-50 volts) of 0.7 secondsindicating that the foam rapidly dissipates a static electric charge.

Formula 1(D)

A polyurethane antistatic foam was prepared using the followingformulation:

    ______________________________________                                        Material                   Parts                                              ______________________________________                                        Niax 16-56 Polyol - a 3000 molecular weight                                                              100                                                propoxylated ethoxylated glycerin polyol                                      manufactured by Union Carbide.                                                TDI 80/20                  50.7                                               L6202 - a silicone surfactant manufactured by Union                                                      1.2                                                Carbide.                                                                      T-120 - dibutyl tin mercaptide, manufactured by                                                          0.5                                                M & T Chemical.                                                               Water                      4.1                                                Polycat 12 Amine Catalyst - a proprietary tertiary                                                       0.8                                                amine manufactured by Air Products and Chemicals.                             5% solution of TCNE in PCF 0.4                                                Carbon Pigment - a 18% dispersion of carbon in a                                                         7.7                                                polyether polyol.                                                             ______________________________________                                    

This foam had a volume resistivity of 4.7 E 11 ohm cm indicating theeffectiveness of in situ TCNE in conferring electrical conductivityproperties to polyurethane foam at low concentrations.

Formula 1(E)

An antistatic 15 ppi polyurethane foam was prepared using a graft polyol(as the hydroxyl bearing constituent) on a commercial foaming machineusing the following formulation:

    ______________________________________                                        Material                   Parts                                              ______________________________________                                        Pluracol 637 - a graft polyol 20% acrylonitrile                                                          100                                                styrene copolymer grafted on a propoxylated                                   ethoxylated glycerin (M W 4200), manufactured by                              BASF.                                                                         TDI 80/20 at 70 °F. 51.8                                               L6202 - a silicone surfactant manufactured by                                                            1.0                                                Union Carbide.                                                                Water                      4.6                                                C-6N - a 33% solution of stannous octoate in                                                             0.07                                               diisononyl phthalate, manufactured by Witco                                   Chemical Corp.                                                                Amine Catalyst 33LV        0.59                                               5% solution of TCNE in PCF 6.0                                                Carbon Pigment - 18% dispersion of carbon in a                                                           4.0                                                polyether polyol.                                                             ______________________________________                                    

The polyol throughput of the foaming machine was 200 lbs/min and themixing head speed was 6000 RPM producing an antistatic graft foam bun221/2" high and 51" wide. The foam bun was cut into ten foot sections.One ten foot long section of this foam bun was thermally reticulatedusing the method and apparatus described in Geen U.S. Pat. No.3,175,025. After thermal reticulation, the foam had a volume resistivityof 3.8 E 10 ohm cm, a surface resistivity of 3.6 E 10 ohms/square andstatic decay (5000-500 volts) times at 15% relative humidity of 0.07seconds and (5000-50 volts) 0.15 seconds demonstrating the excellentantistatic properties of the foam.

Formula 1(F)

A polyurethane foam was prepared by reacting the following ingredientsin a conventional polyurethane foaming process:

    ______________________________________                                        Material                     Parts                                            ______________________________________                                        Poly G 32-52 a propoxylated ethoxylated glycerin                                                           100                                              (M W 3300) manufactured by Olin Chemicals,                                    Stamford, Connecticut.                                                        L-520 - a silicone surfactant manufactured by                                                              1.0                                              Union Carbide.                                                                Water                        3.5                                              Niax A-1 - dimethyl aminoethyl ether 70% in                                                                0.4                                              dipropylene glycol manufactured by Union Carbide.                             TBTO - tributyl tin oxide manufactured by M & T.                                                           0.4                                              10% solution of TCNE in DPG  3.0                                              Lupranate M-10 - a polymeric diphenylmethane                                                               73.3                                             diisocyanate, manufactured by BASF.                                           ______________________________________                                    

After the foam had cooled the volume resistance of the three dimensionalfoam structure was measured. This foam had a volume resistance of1.5×10¹⁰ ohm cm, displaying excellent antistatic properties.

Formula 1(G)

A polyurethane foam was prepared by combining the following reactants:

    ______________________________________                                        Material                   Parts                                              ______________________________________                                        Niax E-576 Polyol - an ethoxylated propoxylated                                                          100                                                glycerin (M W 3700), available from Union Carbide.                            L-564 - a silicone surfactant available from Union                                                       1.0                                                Carbide.                                                                      Water                      4.1                                                T-120 - dibutyl tin mercaptide, manufactured by                                                          0.4                                                M & T Chemicals.                                                              Niax A-4 - a tertiary amine mixture manufactured                                                         1.3                                                by Union Carbide.                                                             5% solution of TCNE in PCF 6.0                                                Isophorone diisocyanate    60.0                                               ______________________________________                                    

This non-reticulated foam had a volume resistivity of 8.2×10⁹ ohm cm.

EXAMPLE 2 Non-Reticulated TCNE Foams A. Preparation

A series of TCNE non-reticulated polyurethane foams were preparedincorporating 0.05, 0.1, 0.2, 0.3, 0.4, 0.6, 1.0 and 2.0 parts of TCNE.The formulations shown in Table II were used in preparing thesenon-reticulated TCNE foams. The appropriate quantity of TCNE was firstdissolved in Tris chloroisopropyl phosphate to make a 5% TCNE solutionand then combined with the other foam forming reactants just prior tofoaming. It was found that increasing amounts of TCNE caused increasedconductivity (i.e. decreased electrical resistance) as shown in FIGS. 1and 2.

                  TABLE I                                                         ______________________________________                                        FOAM FORMULATIONS                                                             Material    Parts                                                             ______________________________________                                        994         50                                                                16-56       50                                                                L6202       1.2                                                               Water       4.6                                                               33LV        0.4                                                               UL29        0.3                                                               TDI (80/20) 51.0                                                              TCNE        (0.05, (0.1), (0.2), (0.3),                                                   (0.4), (0.6), (1.0), and (2.0)                                    ______________________________________                                    

The surface and volume resistivities of the TCNE containing polyurethanefoams made pursuant to Table I were determined and the TCNEconcentration was graphed against the respective electrical resistancevalues, as in FIGS. 1 and 2.

B. Resistivity

After completion of the foaming reaction and cooling of the product toambient temperatures the volume resistivity of the resultingnon-reticulated foam product was measured using the following equipmentand procedures (which are essentially those of ASTM-D-257-78). Acircular guard ring electrode having a center electrode ring (53 mm indiameter) and an outer electrode ring (101 mm in diameter) is placed incontact with a foam specimen. A base electrode (or flat steel plate) isplaced on the opposite side of the foam specimen. The inner (+)electrode and the base (-) electrode are connected to a "Dr. KamphausenMilli To" ohmmeter (Monroe Electronics, Londonville, New York) toproduce a vertical field through the foam specimen between the plates.The guard electrode is connected to the ground. A TCNE foam specimen(approximately 5"×5"×1" thick) is placed between the electrodes, theMilli To voltage set to 500 volts and the variable resistance adjusteduntil a resistance reading is obtained on the meter. After allowing themeter to stabilize for about 1 minute, the resistance of the specimen,the temperature/humidity and the thickness of the specimen are recorded.The volume resistivity is calculated using the following formula##EQU1##

The surface resistance of a foam specimen is measured using the sameapparatus, but with the inner electrode being the anode (+) of the outerelectrode being the cathode (-) and the base plate serving as ground.The surface resistivity is the measured resistance ×10. These tests areconducted according to ASTM D257, a standard for surface resistivitymeasurement.

There are at least three standards for antistatic compounds. Electronicsindustry standard IS-5 requires a static decay rate of a 99% chargedecay in less than two seconds and a surface resistivity of less than1×10¹³ ohms. Military standard MIL-B-81705B is a military specificationfor packaging materials for electrosensitive devices and explosives. Itspecifies that the charge induced by the application of 5000 volts atless than 15% relative humidity must decay completely within 2 seconds.This standard does not have any surface resistivity requirement. TheNational Fire Protection Association standard NFPA-56A-1978 foroperating room products requires that an applied charge drop to 10% ofits initial value within 0.5 seconds, at a relative humidity of 50%.

Static decay is measured according to Federal Test Method Standard 101BMethod 4046. A 5000 volt charge is applied to the surface of thespecimen, the maximum charge accepted is measured, and the time requiredto dissipate the charge after a ground is applied is determined.

These procedures and apparatus were used for the measurements reportedin the Examples.

In this present example, TCNE was found to be a particularly effectiveantistatic agent for graft foam (i.e. foam produced used graft polyols).Use of a grafted polyol (e.g. Pluracol 994) and 0.2 php TCNE producedurethane foam with a volume resistivity of 8.55×10¹⁰ ohm cm.

EXAMPLE 3 Resistance to Extraction and Aging of Non-reticulated TCNEFoam Materials

The permanence of the antistatic properties of the TCNE polyurethanefoam produced in Example 2 was measured by extraction with hot water,extraction in JP-5 (petroleum jet fuel) and also by dry heat aging at300° F., as shown in Table II. The JP-5 extraction test was conducted bycontinuously squeezing a 5"×5"×1" sample of the antistatic foam in JP-5jet fuel for 5 minutes, wringing out the jet fuel, washing 1 minute incold water, and drying at 158° F. The foam was then conditioned at roomtemperature at 50% relative humidity for 16 hours and the surface andvolume resistivities was determined according to ASTM D 257. Theprocedure for testing in hot water was to immerse a foam sample 5"×5"×1"thick in 140° F. water squeezing for 5 minutes, remove the foam, wringout the water, allow the foam to dry at 158° F., condition at 50%relative humidity for 16 hours and then make surface and volumeresistance measurements. Hot air aging was conducted in a hot air oven.After removal from the oven and cooling to ambient temperature the foamwas conditioned at 50% humidity for 16 hours and the volume and surfaceresistivity was determined. The test results are reported in Table II,which indicates that the electrical conductivity conferred on the foamby foaming in situ with TCNE is essentially unaffected in foam materialexposed to hot water and JP-5 jet fuel and that the antistaticproperties resist dry heat aging.

                  TABLE II                                                        ______________________________________                                        TCNE                     Before    After                                      (php) Treatment Conditions                                                                             Treatment Treatment                                  ______________________________________                                              Foam sample 5" × 5" × 1"                                          thick.                                                                  0.4   Squeezed 5 min.                                                               in 140° F. water                                                       Surface Resistivity (ohms/sq.)                                                                   4.40 E 10 9.80 E 10                                        Volume Resistivity (ohm cm)                                                                      2.67 E 10 2.16 E 10                                        Squeezed 5 min. JP-5                                                    0.4   Surface Resistivity (ohms/sq.)                                                                   5.26 E 10 1.90 E 10                                        Volume Resistivity (ohm cm)                                                                      4.02 E 10 9.91 E 9                                         Dry heat aging at 300° F.                                              1. 1 hour                                                               0.1   Surface Resistivity (ohms/sq.)                                                                   1.46 E 12 2.45 E 12                                        Volume Resistivity (ohm cm)                                                                      3.11 E 11 5.77 E 11                                        2. 2 hours                                                              0.2   Surface Resistivity (ohms/sq.)                                                                   1.98 E 11 8.97 E 10                                        Volume Resistivity (ohm cm)                                                                      8.55 E 10 7.66 E 10                                        3. 3 hours                                                              0.2   Surface Resistivity (ohms/sq.)                                                                   1.98 E 11 1.22 E 11                                        Volume Resistivity (ohm cm)                                                                      8.55 E 10 1.05 E 11                                  ______________________________________                                    

EXAMPLE 4 Resistance to Extraction and Aging in ReticulatedTCNE/Polyurethane Foam Samples

The foam products prepared in Example 2 but containing 0.1, 0.2, 0.3 and0.4 php TCNE were thermally reticulated using the process of Geen U.S.Pat. No. 3,175,025 and thereafter samples were subjected to impregnationwith hot water, autoclaving and dry heat aging. Thereafter the surfaceand volume resistivity of the foam samples (5"×5"×1"), each - containingdifferent amounts of TCNE, was tested.

The electrical conductivity of TCNE reticulated foam is not meaningfullyaffected by immersion in hot water, steam or by long exposure to dryheat. TCNE is permanently incorporated into the foam. As shown in TableIII, under the severe conditions of one week autoclaved aging, volumeresistivity remained substantially constant in a foam containing 0.4 phpTCNE.

                  TABLE III                                                       ______________________________________                                        TCNE                     Before    After                                      (php) Treatment Conditions                                                                             Treatment Treatment                                  ______________________________________                                              a. Squeezed 5 min. in                                                         140° F. water                                                    0.3   Surface Resistivity (ohms/sq)                                                                    1.03 E 11 2.10 E 11                                        Volume Resistivity (ohms cm)                                                                     5.05 E 10 1.41 E 11                                        b. Autoclaved 250° F.                                            0.4   1. 5 hours                                                                    Surface Resistivity (ohms/sq)                                                                    5.95 E 10 1.07 E 11                                        Volume Resistivity (ohm cm)                                                                      3.95 E 10 4.08 E 10                                        2. 24 hours                                                             0.4   Surface Resistivity (ohms/sq)                                                                    5.15 E 10 4.10 E 10                                        Volume Resistivity (ohm cm)                                                                      3.06 E 10 2.99 E 10                                        3. 48 hours                                                             0.4   Surface Resistivity (ohms/sq)                                                                    5.15 E 10 2.62 E 10                                        Volume Resistivity (ohm cm)                                                                      3.06 E 10 2.99 E 10                                        4. 72 hours                                                             0.4   Surface Resistivity (ohms/sq)                                                                    5.15 E 10 2.82 E 10                                        Volume Resistivity (ohm cm)                                                                      3.06 E 10 2.18 E 10                                        5. 96 hours                                                             0.4   Surface Resistivity (ohms/sq)                                                                    5.15 E 10 3.32 E 10                                        Volume Resistivity (ohm cm)                                                                      3.06 E 10 1.85 E 10                                        6. 168 hours                                                            0.4   Surface Resistivity (ohms/sq)                                                                    5.15 E 10 1.84 E 10                                        Volume Resistivity (ohm cm)                                                                      3.06 E 10 1.19 E 10                                        c. Dry Heat Aging at 284° F.                                     0.2   1. 24 hours                                                                   Surface Resistivity (ohms/sq)                                                                    1.59 E 11 1.74 E 11                                        Volume Resistivity (ohm cm)                                                                      7.89 E 11 1.03 E 11                                        2. 48 hours                                                             0.2   Surface Resistivity (ohms/sq)                                                                    1.59 E 11 2.72 E 11                                        Volume Resistivity (ohm cm)                                                                      7 89 E 11 1.58 E 11                                        3. 72 hours                                                             0.2   Surface Resistivity (ohms/sq)                                                                    1.59 E 11 3.85 E 11                                        Volume Resistivity (ohm cm)                                                                      7.89 E 11 1.73 E 11                                        4. 96 hours                                                             0.2   Surface Resistivity (ohms/sq)                                                                    1.59 E 11 5.83 E 11                                        Volume Resistivity (ohm cm)                                                                      7.89 E 11 1.29 E 11                                        5. 168 hours                                                            0.2   Surface Resistivity (ohms/sq)                                                                    1.58 E 11 4.26 E 11                                        Volume Resistivity (ohm om)                                                                      7.89 E 11 3.18 E 11                                  ______________________________________                                    

EXAMPLE 5 In Situ Reticulated TCNE Foams

Reticulated foams were prepared containing 0.1, 0.2, 0.3 and 0.4 partsTCNE. Except for TCNE which ranged from 0.1 to 0.4 php (as describedabove) the same formulations were used in these reticulated foams aswere employed in making the non-reticulated foams of Example 2. Thephysical properties of these foam samples are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                                   Parts TCNE                                                                    0.1    0.2      0.3      0.4                                       ______________________________________                                        A. Before Reticulation                                                        Air Flow (cfm)                                                                             0.5      1.0      6.0    7.0                                     Density (pcf)                                                                              1.23 (top)                                                                             1.38 (top)                                                                             1.48   1.36 (top)                              25% CLD (1)  0.52     0.51     0.57   0.54                                    Surface Resistivity                                                                        6.75 E 11                                                                              2.44 E 11                                                                              8.35 E 10                                                                            4.63 E 10                               Volume Resistivity                                                                         2.52 E 11                                                                              9.36 E 10                                                                              4.90 E 10                                                                            3.68 E 10                               After Reticulation                                                            Air Flow (cfm)                                                                             8.0      8.3      8.2    9.6                                     Density (pcf)                                                                              1.50     1.42     1.86   1.97                                    25% CLD      0.42     0.48     0.67   0.67                                    Surface Resistivity                                                                        4.86 E 11                                                                              1.67 E 11                                                                              6.91 E 10                                                                            4.43 E 10                               Volume Resistivity                                                                         1.60 E 11                                                                              6.46 E 10                                                                              5.22 E 10                                                                            3.92 E 10                               Tensile Strength (psi)                                                                     21.1     22.0     24.1   21.5                                    % Elongation 260      270      210    200                                     Tear Strength (psi)                                                                        4.4      --       --     4.7                                     ______________________________________                                         (1) Compression load deflection                                          

Reticulation is not detrimental to the excellent conductive andantistatic properties imparted to polyurethane foam structurescontaining small quantities of TCNE, as shown by the substantiallyunchanged resistivity characteristics of the foam specimens before andafter reticulation. Also, the TCNE did not adversely affect the strengthof the foam.

While not being bound by any specific theory of operation for theinvention it is believed that the resistance to extraction of TCNE,which accepts electrons from nitrogen-containing polymers in the foam,is due to formation of a chemical bond between the skeletal structure ofthe polyurethane and the TCNE during the in situ foam-forming operation.

EXAMPLE 6 Humidity Exposure Test

The electrical (volume) resistance of TCNE containing polyurethane foamsmade as in Example 2 was measured at various relative humidities from 7to 99%.

Volume resistance measurements showed that polyurethane foam made withTCNE is not particularly sensitive to humidity changes. This isillustrated in the results of the humidity exposure test reflected inTable V below. Each foam specimen was exposed to room humidity of 7%,50% and 99% for 16 hours. The foams tested below were samples (5"×5"×1")of the same foams used in Example 5 above.

                  TABLE V                                                         ______________________________________                                               TCNE in Foam (php)                                                            0.1     0.2       0.3       0.4                                        ______________________________________                                        Surface Resistivity (ohms/sq.)                                                7% R.H.  7.38 E 11 2.07 E 11 7.98 E 10                                                                             5.85 E 10                                50% R.H. 3.27 E 11 1.40 E 11 7.00 E 10                                                                             4.34 E 10                                99% R.H. 1.12 E 11 6.17 E 10 3.59 E 10                                                                             2.94 E 10                                Volume Resistivity (ohm cm)                                                   7% R.H.  2.04 E 11 8.23 E 10 6.30 E 10                                                                             4.51 E 10                                50% R.H. 9.07 E 10 4.46 E 10 3.93 E 10                                                                             2.43 E 10                                99% R.H. 2.34 E 10 1.41 E 10 1.29 E 10                                                                             8.07 E 9                                 ______________________________________                                    

EXAMPLE 7 Carbon Black Plus TCNE

The in situ incorporation of carbon black pigment into the foam furtherdecreases its electrical resistance (and increases electricalconductivity), but only if TCNE is also present. This was confirmed byincorporating finely divided carbon black into polyurethane foamcontaining TCNE and prepared from the same constituents as in Example 2but containing 0.1, 0.2, 0.3, 0.4 and 0.5 parts TCNE. FIG. 3 illustratesthe enhanced conductivity of foam containing TCNE and carbon black. Onesuitable method for incorporating carbon in the foam reactants is to usean 18% dispersion of carbon in a polyether polyol (available from PDI asDispersion No. 4824).

The conductivity enhancement realized by incorporation of carbon blackpigment with TCNE was surprising since the incorporation of carbonpigment in reticulated 15 ppi polyurethane foam (80/20 TDI+Pluracol 637)does not appear to lower its resistance value. Several TCNE foams wereprepared containing carbon black to confirm the synergistic effect ofcarbon black and TCNE in decreasing electrical resistance. The volumeresistivity of these foams at different concentrations of TCNE wascompared with that of non-pigmented TCNE foams. As shown in FIG. 3, theincorporation of carbon black pigment and TCNE in polyurethane foamforming ingredients does indeed lower the electrical resistance of theresulting polyurethane foam material beyond the decrease that isattainable with incorporation of TCNE alone.

TCNE is a solid agent, and its dispersion in a polyol yields a foamproduct with holes in the foam. Unless it is dissolved in a suitablesolvent prior to admixture with the other foam forming reactants,combination of TCNE with such materials will not produce an acceptableelectrically conductive three dimensional polyurethane foam product.Therefore, the TCNE must be dissolved in a suitable aqueous or organicsolvent prior to combination with the other foam forming reactants.Water or any of a number of diverse organic solvents may be used todissolve the TCNE, provided they are compatible with the foam materialand do not hinder the foam forming process. Solutions containing between1 and 10% TCNE and preferably 5-10% TCNE yield acceptable foam productsand facilitate combination of TCNE and the other foam formingingredients. Among the useful organic solvents for TCNE are Dipropyleneglycol, Tris chloroisopropyl phosphate, Tris chloroethyl phosphate andTDI. Solutions of TCNE in PCF and CEF caused no detrimental effect onthe electrical conductivity of the resulting foam product. Therefore,PCF and CEF are an especially preferred as TCNE solvents.

EXAMPLE 8

Two reticulated foam products were made pursuant to Example 2 butsubstituted respectively with Pluracol 994 (graft copolymer) andPluracol 637 polyol graft copolymer formulation. The volume resistivityof each sample was measured and is shown in Table VI.

                  TABLE VI                                                        ______________________________________                                        Volume Resistivities of TCNE Foams Prepared                                   With Different Polyol Systems                                                             Parts TCNE                                                        Polyol        0.1        0.2      0.3                                         ______________________________________                                        100% Pluracol 637                                                                           9.50 E 10  3.87 E 10                                                                              2.14 E 10                                   50% Pluracol                                                                  994:50% 16-56 1.25 E 11  3.34 E 10                                                                              2.58 E 10                                   ______________________________________                                    

It can be seen from the data in Table VI that the volume resistivitiesof TCNE foams prepared with the two polyol systems are approximatelyequivalent within the preferred TCNE ranges of the invention. Both 100%Pluracol graft copolymer 637 polyol and a 50:50 blend of Pluracol 994and Niax 16-56 polyol can advantageously be used for the production ofTCNE containing antistatic polyurethane foam.

EXAMPLE 9 Abrasion Resistance of Reticulated TCNE Foams

The resistance of a reticulated foam to mechanical abrasion wasestimated by rubbing a 5"×5"×1" thick sample of a finished foam producton a medium emery paper twenty times. The foam product was made from thefollowing reactants:

                  TABLE VII                                                       ______________________________________                                               Formulation A                                                                           Formulation B                                                                             Formulation C                                           Parts     Parts       Parts                                            ______________________________________                                        Pluracol 637                                                                           100         100         100                                          5% TCNE  2.0         4.0         6.0                                          in PCF                                                                        PDI 4824 7.7         7.7         7.7                                          L6202    1.0         1.0         1.0                                          H.sub.2 O                                                                              4.6         4.6         4.6                                          33LV     0.4         0.4         0.5                                          UL29     0.3         0.3         0.5                                          TDI      51          51          51                                           ______________________________________                                    

The results reported in Table VII(A) indicate that the electricalconductivity property of the TCNE foam is not eliminated orsubstantially diminished by mechanical abrasion.

                  TABLE VII(A)                                                    ______________________________________                                                          Before After                                                                  Abrasion                                                                             Abrasion                                             ______________________________________                                        Formulation A                                                                 0.1 Parts TCNE                                                                Surface Resistivity (ohms/sq)                                                                     2.14 E 11                                                                              1.97 E 11                                        Volume Resistivity (ohm cm)                                                                       7.41 E 10                                                                              6.83 E 10                                        Formulation B                                                                 0.2 Parts TCNE                                                                Surface Resistivity (ohms/sq)                                                                     5.12 E 10                                                                              5.18 E 10                                        Volume Resistivity (ohm cm)                                                                       3.14 E 10                                                                              2.94 E 10                                        Formulation C                                                                 0.3 Parts TCNE                                                                Surface Resistivity (ohms/sq)                                                                     3.49 E 10                                                                              5.31 E 10                                        Volume Resistivity (ohm cm)                                                                       2.65 E 10                                                                              2.67 E 10                                        ______________________________________                                    

EXAMPLE 10 Temperature Resistance

The sensitivity of the electrical resistance values of TCNE foams totemperature was measured on several non-reticulated TCNE containing foamspecimens made pursuant to Table VIII(A).

                  TABLE VIII(A)                                                   ______________________________________                                                           Parts                                                      ______________________________________                                        Niax 16-56           100                                                      L6202                1.2                                                      H.sub.2 O            4.6                                                      UL29                 .4                                                       33LV                 .3                                                       5% Solution of TCNE                                                           in PCF               (0.02) (0.05)                                                                 (0.1) (0.2) (0.3)                                        TDI                  53.2                                                     ______________________________________                                    

Tests were performed at 40° F., 70° F., 158° F., and 300° F. Thereticulated foam formulations contained TCNE ranging from 0.02 to 0.3php. It was discovered that the conductivity of the TCNE foam is onlyslightly better as the temperature of the foam is increased. Forexample, at 0.02 parts TCNE, volume resistivity decreased from 3.52×10¹¹at 40° F. to 1.00×10¹¹ at 300° F.

Table VIII(B) illustrates the slight decrease in volume resistivity withincreased temperature of conventional (non-graft) polyurethane foams.

                  TABLE VIII(B)                                                   ______________________________________                                         The Effect of Temperature on Resistivity of TCNE Foam                        Volume Resistivity (ohm cm)                                                   0.02 parts 0.05 parts                                                                             0.1 parts  0.2 parts                                                                            0.3 parts                               TCNE       TCNE     TCNE       TCNE   TCNE                                    php        php      php        php    php                                     ______________________________________                                        40°  F.                                                                      3.52 E 11                                                                              1.52 E 11                                                                              4.77 E 10                                                                              3.60 E 10                                                                            1.76 E 10                             70°  F.                                                                      3.05 E 11                                                                              1.01 E 11                                                                              3.71 E 10                                                                              2.26 E 10                                                                            1.62 E 10                             158°  F.                                                                     2.94 E 11                                                                              7.95 E 10                                                                              3.51 E 10                                                                              1.66 E 10                                                                            1.44 E 10                             300°  F.                                                                     1.00 E 11                                                                              4.03 E 10                                                                              2.79 E 10                                                                              1.37 E 10                                                                            1.36 E 10                             ______________________________________                                    

A particularly preferred formulation for the TCNE reticulated foam ofthe present invention is:

    ______________________________________                                                         Preferred                                                    Material         Parts                                                        ______________________________________                                        Pluracol 637     100                                                          TCNE             0.2                                                          Fyrol PCF        3.8                                                          L6202            1.0                                                          PDI black #4824  7.7                                                          Water            4.6                                                          33LV             0.4                                                          UL29             0.3                                                          TDI (80/20)      51.0                                                         ______________________________________                                    

Water level of the foam material can be adjusted to give the densityrequired, and can be varied between 1.4 php for a 6 pcf (pounds percubic foot) foam to 5.0 php for a 1.4 pcf foam. Generally, the lower thewater content of a foam material the lower the electrical resistance ofthe foam.

EXAMPLE 11 Electrically Conductive Picric Acid Foams

A wide variety of polyurethane foam compositions containing picric acidand analogs thereof as the charge transfer agent can be prepared, asillustrated below.

Formula 11 (PICRIC ACID)

A polyurethane antistatic foam was prepared by admixing the followingingredients on a conventional polyurethane foaming machine:

    ______________________________________                                        Material                      Parts                                           ______________________________________                                        Poly G 32-52 a propoxylated ethoxylated glycerin                                                            100                                             (M W 3300) manufactured by Olin Chemicals,                                    Stamford, Connecticut.                                                        Picric Acid                   1.0                                             Fyrol PCF                     5.0                                             Water                         3.6                                             Union Carbide Silicone L6202 is a silicone                                                                  1.0                                             surfactant manufactured by Union Carbide.                                     Witco Tin Catalyst UL29 - is Diethyl tin mercaptide                                                         1.5                                             manufactured by Witco Chemical Corp., Chicago, Ill.                           Dabco 33LV - a 33% solution of triethylene diamine                                                          1.2                                             in dipropylene glycol, manufactured by Air Products                           & Chemicals, Inc., Allentown, Pennsylvania                                    TDI 80/20                     43.7                                            ______________________________________                                    

The resulting foam product had a rise time of 120 seconds, a density of1.87 pcf, an airflow of 0.90 cfm, and a surface resistivity of 2.9 E 10ohm/sq. This formula can be varied by replacing picric acid withelectrically conductive analogs, such as those in Formulas 11(A-J), asshown below.

                  TABLE IX                                                        ______________________________________                                        BASIC FOAM FORMULATION                                                                              (php)                                                   ______________________________________                                        32-52                 100                                                     FYROL PCF             5.0                                                     WATER                 3.6                                                     L6202                 1.0                                                     UL29                  1.0                                                     33LV                  1.0                                                     TDI (80/20)           43.7                                                    CHARGE TRANSFER AGENT 1.0                                                     ______________________________________                                    

The following data was obtained for each tested picric acid analog.(Note that FYROL PCF was omitted in Formulas H and J).

    __________________________________________________________________________    SURFACE RESISTIVITY FOR PICRIC ACID ANALOGS                                                           RESISTIVITY                                                                           RISE                                                                              DENSITY                                                                             AIRFLOW                             FORMULA                                                                              CHARGE TRANSFER AGENT                                                                          OHMS/SQ.                                                                              TIME                                                                              PCF   CFM                                 __________________________________________________________________________    A      2,4-DINITROPHENOL                                                                              4.3 E 10                                                                              90 s                                                                              1.79  3.3                                 B      2,5-DINITROPHENOL                                                                              9.1 E 10                                                                              49 s                                                                              1.72  1.79                                C      4-NITROPHENOL    1.0 E 11                                                                              37 s                                                                              1.68  0.12                                D      4-CYANOPHENOL    1.4 E 11                                                                              34 s                                                                              1.70  0.14                                E      3-NITROPHENOL    2.0 E 11                                                                              28 s                                                                              1.66  0.08                                F      2,4-DINITROANISOL                                                                              2.4 E 11                                                                              36 s                                                                              1.62  0.15                                G      2-NITROPHENOL    4.3 E 11                                                                              30 s                                                                              1.64  0.31                                H      2-HYDROXYACETOPHENONE                                                                          4.8 E 11                                                                              26 s                                                                              1.58  0.18                                I      4-HYDROXYACETOPHENONE                                                                          5.4 E 11                                                                              31 s                                                                              1.65  0.15                                J      METHYL SALICYLATE                                                                              1.4 E 12                                                                              30 s                                                                              1.63  0.09                                CONTROL                                                                              NONE             2.4 E 12                                                                              30 s                                                                              1.58  0.14                                __________________________________________________________________________

All of these exemplary picric acid analogs exhibit effective antistaticproperties, except methyl salicylate. Typical surface resistivity valuesfor picric acid and its analogs is about 5.6 E 10 ohm/sq. for 0.5 php,and 2.4 E 12 for 1.0 php of charge transfer agent. When no picric acidanalog is used, the resistivity is about 2.9 E 10.

Although most of the formulations in the above examples use PCF as asolvent for picric acid, or an antistatic analog thereof, other solventscan also be used. For example, generally equivalent results are obtainedusing 16.7% picric acid in Fyrol CEF or Dipropylene glycol, or 25%picric acid in Thermolin 101 or Antiblaze 100.

EXAMPLE 12 Additional Antistatic Picric Acid Formulations

A number of additional foam formulations and picric acid analogs havebeen tested, and exhibit antistatic properties.

Formula 12(A)

A polyurethane foam was prepared by admixing the following ingredientson a conventional polyurethane foaming machine:

    ______________________________________                                        Material                  Parts                                               ______________________________________                                        Pluracol 718 - a standard 3000 molecular weight                                                         100                                                 ethoxylated propoxylated glycerin polyol                                      manufactured by BASF.                                                         Silicone L520 is a silicone surfactant                                                                  1.0                                                 manufactured by Union Carbide Corp.                                           Water                     4.1                                                 T-120 Dibutyl tin mercaptide, manufactured                                                              1.2                                                 by M&T Chemicals, Inc., Rahway, N.J.                                          Niax A-4, a tertiary amine mixture made by                                                              1.2                                                 Union Carbide Corp.                                                           16% solution of picric acid in Fyrol                                                                    6.0                                                 PCF-tri(chloropropyl) Phosphate, made by                                      Stauffer Chemical Co., Westport, CT.                                          TDI 80/20                 49.3                                                ______________________________________                                    

The resulting foam product has a surface resistivity of 1.6 E 9ohms/square.

Formula 12(B)

A polyurethane antistatic foam was prepared by admixing the followingingredients in a conventional polyurethane foaming process:

    ______________________________________                                        Material                  Parts                                               ______________________________________                                        Poly G 32-52, A propoxylated ethoxylated                                                                100                                                 glycerin (MW 3300) made by Olin Chemicals                                     Silicone L6202, a silicone surfactant                                                                   1.0                                                 manufactured by Union Carbide Corp.                                           Water                     4.3                                                 T-125 Dibutyl tin dialkyl acid, made                                                                    1.0                                                 by M&T Chemicals, Inc., Rahway, N.J.                                          Niax A-1, Dimethyl aminoethyl ether 10% in                                                              1.0                                                 dipropylene glycol, made by Union Carbide                                     16.7% solution of picric acid in Fyrol PCF                                                              3.0                                                 Lupranate M-10, a polymeric diphenylmethane                                                             73.3                                                diisocyanate made by BASF.                                                    ______________________________________                                    

After cooling, the resulting three-dimensional foam product has asurface resistivity of 1.65 E 11 ohms/square, demonstrating excellentantistatic properties.

Formula 12(C)

A polyurethane antistatic ester foam was prepared by admixing thefollowing ingredients in a conventional polyurethane foaming process:

    __________________________________________________________________________    Material             l     2     3                                            __________________________________________________________________________    Fomrez 76, a hydroxyl terminated ester                                                             100   100   100                                          specifically glycerine adipate poly-                                          oxyethylene, made by Witco Chemical.                                          N--cocomorpholine    1.5   1.5   1.5                                          Thancat M-75, a tertiary amine blend                                                               1.8   1.8   1.8                                          made by Texaco Chemical Co.                                                   Water                4.0   4.0   4.0                                          L-536, a silicon surfactant made by                                                                0.7   0.7   0.7                                          Union Carbide Corp.                                                           Fomrez M66-82A, a mixture of                                                                       0.6   0.6   0.6                                          surfactants made by Witco                                                     Fomrez YA 49-49, an organic hydroxyl                                                               0     4.0   4.0                                          terminated ester crosslinker, made                                            Witco Chemical.                                                               16% solution of picric acid in Fyrol PCF                                                           3.0   6.0   9.0                                          TDI 80/20            52.7  52.7  52.7                                         SURFACE RESISTIVITY (OHM/SQ.)                                                                      2.5 E 11                                                                            1.4 E 11                                                                            1.0 E 11                                     VOLUME RESISTIVITY (OHM CM)                                                                        1.0 E 11                                                                            6.0 E 10                                                                            3.5 E 10                                     __________________________________________________________________________

These examples illustrate the excellent antistatic properties of esterfoams containing picric acid.

Formula 12(D)

A series of antistatic ether foams were prepared as follows, withamounts given as parts per hundred polyol (php).

    __________________________________________________________________________    MATERIAL      1    2    3    4    5    6                                      __________________________________________________________________________    Niax 16-56    100  100  100  100  100  100                                    L6202         1.1  1.1  1.0  1.0  0.9  0.9                                    Water         4.7  4.7  4.1  4.1  3.4  3.4                                    Fomrez UL29   0.8  1.2  0.8  1.5  0.8  1.2                                    Dabco 33LV    0.8  1.2  0.8  1.2  0.8  1.2                                    16% Picric Acid/PCF                                                                         3.0  6.0  3.0  6.0  3.0  6.0                                    Methylene chloride                                                                          5.0  5.0  0    0    0    0                                      TDI (80/20)   60.6 60.6 49.3 49.3 47.0 47.0                                   DENSITY (PCF) 1.25 1.25 1.62 1.65 1.82 1.83                                   SURFACE RESISTIVITY                                                                         7.4 E 11                                                                           7.4 E 10                                                                           6.0 E 10                                                                           3.2 E 10                                                                           5.6 E 10                                                                           2.8 E 10                               STATIC DECAY  1.0  0.3  0.3  .sub.= 0.1                                                                         0.4  .sub.= 0.2                             __________________________________________________________________________

Niax 16-56 is a 3000 molecular weight polyol, manufactured by UnionCarbide Corp. The surface resistivity is measured as ohm/square. Thestatic decay was measured at 5000-50 volts (sec), and the relativehumidity was 15%.

It has been observed that as the density of these foams increase, thesurface resistivity decreases. All of these foams meet the electricalspecifications of MIL B-81705B for packaging materials for electrostaticdevices and explosives.

Formula 12(E)

A series of graft foams were prepared as follows, with amounts given asparts per hundred polyol (php).

    __________________________________________________________________________    MATERIAL      1    2    3    4    5    6                                      __________________________________________________________________________    Pluracol 994  50   50   50   50   90   90                                     Niax 16-56    50   50   50   50   10   10                                     L6202         1.0  1.0  0.9  0.9  0.7  0.7                                    Water         5.0  5.0  4.5  4.5  2.75 2.75                                   Dabco 33LV    0.7  1.1  0.8  1.2  0.7  1.1                                    Fomrez UL29   0.6  1.0  0.8  1.2  0.7  1.1                                    16% Picric Acid in PCF                                                                      3.0  6.0  3.0  6.0  3.0  6.0                                    TDI (80/20)   57.8 57.8 55.1 55.1 35.8 35.8                                   DENSITY (PCF) 1.16 1.25 1.40 1.41 2.10 2.20                                   SURFACE RESISTIVITY                                                                         1.6 E 11                                                                           8.4 E 10                                                                           3.1 E 11                                                                           1.8 E 11                                                                           9.7 E 10                                                                           3.5 E 10                               STATIC DECAY  1.2  0.6  1.3  0.8  0.8  0.3                                    __________________________________________________________________________

Pluracol 994 is a graft polyol of 40% acrylonitrile styrene copolymergrafted on an ethoxylated propoxylated glycerine (MW 5600), manufacturedby BASF. The surface resistivity is measured as ohm/square. The staticdecay is measured at 5000-50 volts (sec), and the relative humidity was15%.

These picric acid graft foams exhibit excellent antistatic properties.

Formula 12(F)

A series of picric acid foams were prepared according to the followingbasic formulation, with varying amounts of picric acid.

    ______________________________________                                        Pluracol 637        100                                                       L6202               1.0                                                       Water               4.6                                                       Dabco 33LV          0.2-1.4                                                   Fomrez UL29         0.3-1.5                                                   16.7% picric acid in PCF                                                                          0.1-12                                                    TDI 80/20           49.8                                                      ______________________________________                                    

Pluracol 637 is a 20% acrylonitrile styrene copolymer grafted to anethoxylated propoxylated glycerin polyol (MW 4200), manufactured byBASF.

These foams exhibited the following resistivities:

                  TABLE X                                                         ______________________________________                                                PICRIC ACID VOLUME RESISTIVITY                                        FOAM    (php)       (OHM CM)                                                  ______________________________________                                        1       0.017       5.0 E 12                                                  2       0.034       1.9 E 12                                                  3       0.05        5.9 E 11                                                  4       0.10        2.0 E 11                                                  5       0.20        1.1 E 11                                                  6       0.30        6.4 E 10                                                  7       0.40        4.4 E 10                                                  8       0.50        2.5 E 10                                                  9       1.0         1.7 E 10                                                  10      1.5         1.4 E 10                                                  11      2.0         1.1 E 10                                                  ______________________________________                                    

This example illustrates the excellent antistatic properties that can beobtained in picric acid foams at low concentrations. As shown in FIG. 4,as the concentration of picric acid in the foam rises, the decrease inresistivity decreases.

Formula 12(G)

Fire retardant antistatic foam were prepared using picric acid using thefollowing formulations:

    ______________________________________                                                            Parts                                                     Material              1        2                                              ______________________________________                                        Poly G 32-52          100      100                                            L-5750                1.0      1.0                                            Water                 4.7      4.7                                            Dabco 33LV            0.8      0.8                                            Fomrez UL29           0.8      0.8                                            Methylene Chloride    5.0      5.0                                            16.7% picric acid in Fyrol PCF                                                                      3.0      3.0                                            Thermolin 101         15.0     0                                              Antiblaze 100         0        15.0                                           TDI 80/20             61.0     59.4                                           DENSITY (PCF)         1.25     1.25                                           AIR FLOW (CFM)        1.4      1.0                                            ASTM D-1692           S.E.     S.E.                                           SURFACE RESISTIVITY (ohms/sq.)                                                                      4.7 E 10 4.4 E 10                                       ______________________________________                                    

L5750 is a silicone surfactant manufactured by Union Carbide Corp.Thermolin 101 is Tetrakis (2-chloroethyl) diphosphate, manufactured byOlin. Antiblaze 100 is a chloroalkyl diphosphate ester, made by MobilChemical Co.

This example shows the excellent antistatic properties of flameretardant foams containing picric acid.

Formula 12(H)

A prepolymer was made using the following formulations:

    ______________________________________                                               Material Parts                                                         ______________________________________                                               Pluracol 994                                                                           50                                                                   Poly G 32-52                                                                           50                                                                   TDI 80/20                                                                              30                                                            ______________________________________                                    

This prepolymer had a Brookfield viscosity of 8000 cps. It was used toprepare a picric acid antistatic foam using the following formulation.

    ______________________________________                                        Material              Parts                                                   ______________________________________                                        Prepolymer            130                                                     L6202                 1.0                                                     Water                 4.6                                                     Dabco 33LV            1.0                                                     Fomrez UL29           0.5                                                     16.7% picric acid in Fyrol PCF                                                                      3.0                                                     TDI 80/20             20.8                                                    ______________________________________                                    

This foam had the following resistivities:

    ______________________________________                                        SURFACE RESISTIVITY (ohms/square)                                                                       2.5 E 11                                            VOLUME RESISTIVITY (ohms cm)                                                                            6.8 E 10                                            ______________________________________                                    

These foams have good antistatic properties and can be prepared using aprepolymer technique, as well as a "one shot" method.

EXAMPLE 13 Hot Water Extraction

Foam 7 from Formula 12(F) (TABLE X) was washed for 5 minutes in 140° F.water. While washing, the foam was compressed and relaxed under the hotwater to insure maximum water extraction of the antistatic agent. Thefoam was then dried for 3 hours at 158° F. and conditioned for 16 hoursat 75° F. and 50% relative humidity before measurement of itsresistivity. The results are shown in Table XI.

                  TABLE XI                                                        ______________________________________                                        CONDITIONS   VOLUME RESISTIVITY (OHMS CM)                                     ______________________________________                                        No treatment 4.4 E 10                                                         1 Hot water wash                                                                           1.4 E 11                                                         2nd Hot water wash                                                                         2.4 E 11                                                         ______________________________________                                    

These data indicate that picric acid is only slowly extracted from thefoam by hot water.

EXAMPLE 14 Cold Water Extraction

A sample of foam 9 from Formula 12(F) (Table X) was submerged in waterand placed in a 160° F. oven. This foam was removed weekly, dried,conditioned and its resistivity was measured. The water was changedweekly. Following are the results of this test.

                  TABLE XII                                                       ______________________________________                                        CONDITIONS  VOLUME RESISTIVITY (OHMS CM)                                      ______________________________________                                        Unaged      1.7 E 10                                                          1 week      2.1 E 10                                                          2 weeks     6.1 E 10                                                          3 weeks     9.1 E 10                                                          4 weeks     1.7 E 11                                                          ______________________________________                                    

These data indicate that the picric acid was slowly extracted from thefoam by water.

EXAMPLE 15 Graft Foams

Graft antistatic foams were prepared using the following formulations:

    ______________________________________                                                           Parts                                                      Material             1        2                                               ______________________________________                                        Pluracol 637         100      100                                             L6202                1.0      1.0                                             Water                4.4      4.4                                             Dabco 33LV           1.0      1.0                                             Fomrez UL29          1.4      1.2                                             16.7% picric acid in Fyrol PCF                                                                     6.0      0                                               25% picric acid in Thermolin 101                                                                   0        4.0                                             Forest green         2.0      2.0                                             TDI 80/20            51.8     49.8                                            DENSITY (PCF)        1.42     1.45                                            AIR FLOW (CFM)       1.10     1.50                                            VOLUME RESISTIVITY   7.2 E 10 3.9 E 10                                        (ohms/sq.)                                                                    ______________________________________                                    

Forest green is a pigment dispersion No. 4474, manufactured by PigmentDispersions Inc., Edison, N.J.

These foams were reticulated and their resistivity was measured:

    ______________________________________                                        VOLUME RESISTIVITY (ohm cm)                                                                        5.0 E 10  4.3 E 10                                       ______________________________________                                    

These data indicate that there is no loss in conductive propertiescaused by the thermal reticulation process.

EXAMPLE 16 Endurance Tests

The reticulated foams of the previous Example were exposed to thefollowing treatments and their resistivity was measured:

    ______________________________________                                                           1      2                                                   ______________________________________                                        1.    5 min extraction in methylene                                                                    2.7 E 11 2.7 E 11                                          chloride                                                                2.    Dry heat aging 3 hrs 300° F.                                                              5.5 E 10 5.0 E 10                                    3.    Water extraction at 158° F.                                            1 week             6.1 E 11 4.5 E 11                                          2 weeks            1.3 E 12 8.4 E 11                                          3 weeks            4.5 E 12 3.0 E 12                                    ______________________________________                                    

These data indicate that picric acid is slowly extracted by water,extracted by methylene chloride and essentially unaffected by dry heataging.

EXAMPLE 17 Comparative Example

A flexible antistatic foam was made using the following ingredients:

    ______________________________________                                        Material           Parts                                                      ______________________________________                                        Pluracol 994LV     50                                                         Niax 16-56         50                                                         Larostat 377 DPG   5.0                                                        Thermolin 101      5.0                                                        B8028              1.0                                                        Water              3.4                                                        Niax A-10          0.3                                                        Dimethyl benzyl amine                                                                            0.8                                                        T-12               0.1                                                        Methylene chloride 4.0                                                        TDI 80/20          44.5                                                       ______________________________________                                    

Larostat 377 DPG is an alkyl dimethyl ammonium ethosulfate dissolved indipropylene glycol, manufactured by Jordon Chemical Co., Folcroft, PA.B8028 is a silicone surfactant, manufactured by Goldschmidt ChemicalCorp., Hopewell, VA. Niax A-10 is an amine glycol mixture, manufacturedby Union Carbide Corp. T-12 is dibutyl tin dilaurate, manufactured by M& T Chemicals Inc.

This foam had a surface resistivity of 1.8 E 11 ohms/square. The foamwas reticulated. After reticulation, this foam had a surface resistivityof 3.5 E 11 ohms/square.

The reticulated foam containing the quaternary amine antistatic agentwas extracted with water and methylene chloride with the followingresults:

    ______________________________________                                                       SURFACE RESISTIVITY                                                           (ohms/sq.)                                                     ______________________________________                                        5 min methylene chloride                                                                       1.1 E 12                                                     5 min cold water 7.9 E 11                                                     ______________________________________                                    

These data indicate that the quaternary amine is rapidly extracted withwater and methylene chloride.

EXAMPLE 18 Additional Analogs

Various picric acid analogs were evaluated as antistatic charge transferagents, as shown below:

TABLE XIII

1. 1 part 4-nitroanisole in 5 parts Fyrol CEF

2. 1 part 4-aminoacetophenone in 5 parts Fyrol CEF

3. 1 part 4-nitrobenzyl alcohol in 5 parts Fyrol CEF

4. 1 part 2-nitroaniline in 5 parts Fyrol CEF

5. 1 part 2,4-dihydroxyacetophenone in 5 parts Fyrol CEF

6. 1 part 4-nitrocatechol in 5 parts Fyrol PCF

7. 1 part 4-nitro-1-naphthol in 43.7 parts TDI

8. 1 part 4-nitrobenzophenone in 43.7 parts TDI

9. 1 part 4-nitrobenzaldehyde in 43.7 parts TDI

10. 1 part 5-nitroanthranilonitrile in 5 parts dimethyl formamide (DMF)

11. 1 part 2,6-dinitrocresol in 5 parts Fyrol CEF

12. 1 part 4-nitroaniline in 5 parts DMF

13. 1 part 2,4-dinitroaniline in 5 parts DMF

14. 2-nitroanisole-liquid used directly

15. 1 part 4-nitrobenzonitrile in 5 parts DMF and 10 parts CEF

16. 1 part 4-nitroacetanilide in 5 parts DMF

17. 1 part 2,4-dinitro-1-napthol sodium salt dihydrate (Martius yellow)in 7.5 parts DMF

These preparartions were incorporated in foams using 1 php of the analogto be evaluated.

The following foam formulation was used:

    ______________________________________                                        Material          Parts                                                       ______________________________________                                        32-52             100                                                         L6202             1.0                                                         Water             3.4                                                         Evaluated Compound                                                                              1.0                                                         Dabco 33LV        0.5-1.0                                                     UL29              1.0                                                         TDI               43.7                                                        ______________________________________                                    

These foams had the properties shown in Table XIV.

                                      TABLE XIV                                   __________________________________________________________________________                                     Temp.                                                       Rise                                                                             Air      Surface                                                                             (F)                                                         Time                                                                             Flow                                                                              Density                                                                            Resistivity                                                                         % Relative                                   Additive       (sec)                                                                            (cfm)                                                                             (pct)                                                                              (ohms/sq)                                                                           Humidity                                     __________________________________________________________________________      4-nitroanisol                                                                              26 0.3 1.7  6.1 E 11                                                                            74/45                                          4-aminoacetopheone                                                                         28 0.26                                                                              1.7  9.2 E 11                                                                            74/45                                          4-nitrobenzyl alcohol                                                                      27 0.4 1.7  6.7 E 11                                                                            74/45                                          2-nitroaniline                                                                             25 0.5 1.7  3.9 E 11                                                                            74/45                                          2,4-dihdroxyacetophenone                                                                   27 0.25                                                                              1.7  4.4 E 11                                                                            74/45                                          4-nitrocatechol                                                                            54 0.4 1.9  8.0 E 10                                                                            74/45                                          2-nitro-1-naphthol                                                                         27 0.21                                                                              1.6  1.0 E 12                                                                            74/45                                          4-nitrobenzophenone                                                                        29 0.14                                                                              1.8  1.9 E 12                                                                            74/45                                          4-nitrobenzaldehyde                                                                        30 0.09                                                                              1.6  1.0 E 12                                                                            74/45                                        10.                                                                             5-nitroanthranilonitrile                                                                      2.3 1.7  4.9 E 11                                                                            74/40                                          2,6-dinitrocresol                                                                          119                                                                              3.3 1.9  1.4 E 11                                                                            74/40                                          4-nitroaniline                                                                             42 6.3 1.7  6.4 E 11                                                                            74/40                                          2,4-dinitroaniline                                                                         38 3.8 1.6  3.6 E 11                                                                            74/40                                          2-nitroanisole                                                                             54 0.35                                                                              1.7  1.4 E 12                                                                            74/40                                          4-nitrobenzonitrile                                                                        50 1.21                                                                              2.1  1.5 E 11                                                                            72/43                                          4-nitroacetanilide                                                                         41 1.45                                                                              1.9  4.3 E 11                                                                            72/43                                          2,4-dinitro-1-naphthol                                                                     36 2.35                                                                              1.8  2.3 E 10                                                                            72/43                                          sodium salt dihydrate                                                         (Martius Yellow)                                                            __________________________________________________________________________

Of these seventeen compounds, all but four easily reduced the surfaceresistivity below 1 E 12, but none of the compounds evaluated were aseffective as picric acid (2.9 E 10), which has an effective range ofabout 0.015 (0.02) to 2.5 php in urethane form.

EXAMPLE 19

Both 4-nitrophenol and 2,4-dinitrophenol exhibit antistatic propertiesin urethane foam. Foams were prepared using the following formulation:

    ______________________________________                                        Material              Parts                                                   ______________________________________                                        32-52                 100                                                     L 6202                1.0                                                     Water                 3.4                                                     4-nitrophenol or                                                              2,4 dinitrophenol     0.5, 1.0, 2.0                                           Dabco 33LV            0.3, 1.0, 1.2                                           UL29                  0.2, 1.0, 1.5                                           TDI 80/20             43.7                                                    ______________________________________                                    

The surface resistivity of these foams was:

    ______________________________________                                        Surface Resistivity (ohms/square)                                                        0.5php   1.0php    2.0php                                          ______________________________________                                        2,4 dinitrophenol                                                                          2.0 E 11   4.3 E 10  1.3 E 10                                    4-nitrophenol                                                                              2.0 E 11   1.0 E 11  5.2 E 10                                    Picric Acid-control                                                                        5.6 E 10   2.9 E 10                                              ______________________________________                                    

These compounds show antistatic properties in urethane foam, whichincreases as their concentration increases.

EXAMPLE 20 Rebonded Foam

An antistatic rebonded foam having applications as a package foam forsensitive electronic equipment was prepared, with picric acid as anantistatic agent.

A prepolymer was prepared using the following materials:

    ______________________________________                                               Material Parts                                                         ______________________________________                                               Poly G 32-52                                                                           337                                                                  TDI      120                                                           ______________________________________                                    

Thirty grams of shredded foam were sprayed with 42 grams of thefollowing mixture:

    ______________________________________                                        Material             Parts                                                    ______________________________________                                        Prepolymer           6                                                        16.7 picric acid in Fyrol PCF                                                                      6                                                        Methylene Chloride   30                                                       ______________________________________                                    

The prepolymer antistatic coated foam was then sprayed with water whilethe foam was mixing.

The foam was compressed and cured 5 minutes at 210° F., 30 minutes at160° F. and taken out of the mold. The rebonded foam article was thengiven a final 5 minute cure at 210° F.

This rebonded foam had the following properties.

    ______________________________________                                        DENSITY (PCF)          3.1                                                    SURFACE RESISTIVITY (ohms/sq.)                                                                       1.3 E 10                                               ______________________________________                                    

This example illustrates the excellent antistatic properties of arebonded foam containing picric acid.

It has been found that foaming with in situ TCNE, picric acid andanalogs thereof produces adequate antistatic properties in conventionalfoams with as little as about 0.02 php of the charge transfer agent.Foams made with graft polyols preferably have approximately at least 0.1php to achieve acceptable electrical conductivity when TCNE is thecharge transfer agent. With graft polyol foams containing up to 2.5 phpof charge transfer agent (e.g., TCNE), the electrical resistivity of thefinished foam decreases as the level of agent is increased, but the rateof decrease declines as the level increases. As with other polyurethanefoam products, the amount of TDI employed in the foam forming reactiondepends on the hydroxyl number of the polyol and the amount of water inthe formulation.

Although thermal reticulation of the foam products is preferred (due tocost and speed consideration) the other reticulation techniques that arewell known in the art including, for example, immersion of the foam indilute alkaline solution and exposure to high pressure water and ultrasound may also be used to reticulate conductive foams made with thecharge transfer agents, according to the invention.

The electrically conductive foam materials of the present invention maybe employed in a variety of military, industrial and consumerapplications. When shaped in the appropriate configuration and sized tothe proper dimension charge transfer agent containing polyurethane foamproducts can be used for example as packaging material for voltagesensitive computer parts to protect them against static electricdischarges (e.g. Large Scale Integrated Circuits), in medicalapplications (e.g. as grounding mats for operating room equipment) or asan antistatic carpet underlayer. A particularly preferred applicationfor the three-dimensional reticulated charge transfer agent containingfoam materials of the present invention is as a filler material invehicular fuel tanks and especially those installed in military aircraftor racing cars.

What is claimed is:
 1. A three dimensional electrically conductiveplastic foam structure comprising a polyurethane foam containing aneffective amount for lowering the volume resistivity of said foam oftetracyanoethylene.
 2. A three dimensional electrically conductivestructure according to claim 1, wherein said structure is prepared byreacting a polyol and an isocyanate and comprises 0.02 to 2.5 parts perhundred parts by weight of said polyol of said tetracyanoethylene.
 3. Athree dimensional electrically conductive structure according to claim 2wherein said polyurethane foam comprises a reticulated polyurethanefoam.
 4. A three dimensional electrically conductive structure accordingto claim 3, wherein the polyurethane foam comprises at least one graftpolyol reacted with an isocyanate in the presence of saidtetracyanoethylene.
 5. A three dimensional electrically conductivestructure according to claim 4, wherein said tetracyanoethylene isdissolved in a suitable solvent prior to reaction with said polyol andsaid isocyanate.
 6. A three dimensional electrically conductivestructure according to claim 3, wherein the polyurethane foam is formedfrom a graft polyol comprising a copolymer of styrene and acrylonitrilegrafted to an ethylene oxide propylene oxide ether of glycerin.
 7. Athree dimensional electrically conductive structure according to claim6, wherein the polyurethane foam is formed from 0.02 to 2.5 partstetracyanoethylene in a foam compatible organic solvent, 0 to 2.2 partscarbon black, 1 to 8 parts water, in parts per hundred parts of saidpolyol.
 8. A three dimensional electrically conductive structureaccording to claim 7, prepared from foam reactants containing at leastone catalyst.
 9. A three dimensional electrically conductive structureaccording to claim 8 wherein the solvent is a member selected from thegroup consisting of dipropylene glycol, chloroisopropyl phosphate andTris-chloroethyl phosphate, and containing from 2 to 10 percent of saidsolvent of tetracyanoethylene.
 10. A three dimensional electricallyconductive structure according to claim 3, wherein the polyurethane foamhas a void volume greater than 80%.
 11. A three dimensional electricallyconductive structure according to claim 3, wherein the polyurethane foamhas a void volume greater than 90%.
 12. A three dimensional electricallyconductive structure according to claim 11, wherein the effective amountof tetracyanoethylene is from 0.1 to 1.5 parts per hundred parts ofpolyol.
 13. A three dimensional electrically conductive structure havinga volume resistivity of less than 10¹² ohm cm, comprisinga polyurethanefoam containing an effective amount for reducing the electricalresistance of said foam to less than 10¹² ohm cm of tetracyanoethyleneincorporated into said foam in situ.
 14. A three dimensionalelectrically conductive plastic foam structure according to claim 13,wherein said tetracyanoethylene is in an amount ranging from 0.02 to 2.5php.
 15. A three dimensional electrically conductive structure accordingto claim 14, additionally comprising finely divided carbon black pigmentincorporated into said foam in situ.
 16. A three dimensionalelectrically conductive structure according to claim 13, wherein saidpolyurethane foam is thermally reticulated by momentary exposure to anignited combustible gas in a sealed chamber.
 17. A method of preparingan electrically conductive polyurethane foam composition whichcomprises:reacting at least one polyester or polyether polyol with anisocyanate compound in the presence of an effective amount for loweringthe electrical resistance of said polyurethane foam oftetracyanoethylene under foam forming conditions.
 18. A method accordingto claim 17 wherein said electrically conductive polyurethane foam hasan electrical resistance of less than 10¹² ohm cm.
 19. A methodaccording to claim 18, wherein said tetracyanoethylene is present in anamount of 0.2 to 2.5 php.
 20. A method according to claim 18, whereinsaid tetracyanoethylene is present in an amount of 1.0 to 1.5 php.
 21. Amethod according to claim 18, wherein said polyol comprises a graftpolyol.
 22. A method of according to claim 18, which comprises addingfinely divided carbon black pigment to said foam reactants prior to orduring said reacting step.
 23. A method according to claim 21, whereinthe isocyanate compound comprises toluene diisocyanate, the effectiveamount of tetracyanoethylene ranges from between about 0.02 to about 2.5parts per hundred parts polyol dissolved in a polyurethane foamcompatible solvent.
 24. A method of preparing an electrically conductivepolyurethane foam composition having an electrical resistance of 10¹²ohm cm or less comprising the steps of:reacting at least one graftpolyol with toluene diisocyanate in the presence of water, an aminecatalyst, a tin catalyst, a cell control agent and an effective amountfor lowering the electrical resistance of said foam oftetracyanoethylene in a suitable solvent under foam forming conditions;and reticulating said foam to a void volume of more than 80%.
 25. Athermosetting plastic foam composition having a volume resistivity of10¹² ohm cm or less comprising the product obtained by reacting a polyolreactant selected from the group consisting of polyester polyols,polyether polyols, mixtures of polyether and polyester polyols andmixtures of polyether polyols and copolymer polyols with an isocyanatereactant in the presence of tetracyanoethylene.
 26. A foam compositionaccording to claim 25, wherein said product is reticulated and has avoid volume of at least 80%.
 27. The foam composition of claim 25wherein said foam is non-reticulated open cell foam.
 28. The foamcomposition of claim 26 wherein said polyol is a polyether polyol. 29.The foam composition of claim 26 wherein said polyol is a mixture of apolyether polyol and a copolymer polyol.
 30. The foam composition ofclaim 26 wherein said foam has a void volume of more than 90%.